Muharram, the first month of the Islamic calendar, is one of the four sacred months mentioned in the Glorious Qur’ăn:

From out of the four sacred months, Muharram has been blessed with certain specific virtues. The noble Prophet (peace be upon him) said, “The best of fasts besides the month of Ramadhăn is the fasting of Allah’s Month of Muharram and the best of salăt besides the fardh (compulsory) salăt is the tahajjud salăt (performed after midnight before dawn).” (Muslim)

In another Hadeeth, Ibne ‘Abbăs :ra: reports that the Messenger of Allah said, "He who fasts on the day of Arafah (9th Zul Hijjah), his fast will be a compensation for the sins of two years and one who keeps a fast in the month of Muharram will receive the reward of thirty fasts for each fast." (Tabrăni, at-Targheeb wat-Tarheeb)

THE DAY OF ĂSHOORĂ (10th MUHARRAM)

Ibne ‘Abbăs :ra: says, "I did not see Rasoolullah anxiously await the fast of any day, which he gave preference to over other days, but this day, the day of Ăshooră." (Bukhări)

In another Hadeeth, Ibne ‘Abbăs :ra: narrates that the noble Prophet came to Madeenah and found the Jews fasting on the day of Ăshooră. Hence the noble Prophet inquired of them, "What is (the significance of) this day on which you fast?" They replied, "This is a great day. On this day Allah saved Moosă :as: and his people and drowned Fir‘awn and his nation. Thus Moosă fasted on this day as a token of thanksgiving, therefore we too fast on this day." The Messenger of Allah said, "We are more worthy of Moosă and nearer to him than you." Thereafter, the noble Prophet fasted on this day and ordered (his companions) that a fast be kept on this day. (Muslim)

RECOMMENDED DEEDS ON THE DAY OF ĂSHOORĂ
1. The noble Prophet has exhorted and encouraged his Ummah to fast on this day. Aboo Qatădah :ra: narrates that the noble Prophet was asked regarding the fast of the day of Ăshooră. The noble Prophet replied, "It is a compensation for the (minor) sins of the past year." (Muslim)

NOTE: It must be borne in mind that wherever a promise of forgiveness of sins is made upon the fulfilment of some action, it is only the minor sins that are forgiven.

The major sins are not forgiven without true tawbah (repentance).

2. One should also observe the fast of the 9th or 11th Muharram to safeguard his deed from resemblance with the non-Muslims who fast only on the 10th Muharram. Ibne ‘Abbăs :ra: said, "When Rasoolullah observed the fast of the day of Ăshooră and ordered (his companions) to fast, they said, ‘O Rasoolullah! It is a day revered by the Jews and Christians.’ Rasoolullah s said, ‘The coming year, if Allah wills, we will fast on the ninth (also)." (Muslim)

Ibne ‘Abbăs :ra: reports that Rasoolullah said, "Should I live until the coming year, I will definitely fast on the ninth (also)." (Muslim)

The noble Prophet said, "Observe the fast of Ăshooră and oppose the Jews. Fast a day before it or a day after." (Bayhaqi)

Hence, it is important to either fast on the ninth and tenth of Muharram or the tenth and eleventh. To fast only on the day of Ăshooră is makroohe tanzeehi as stated by ‘allămah Ibne Ăbideen Shămi rahmatullăhi alayh.

3. One should be generous on one’s family and dependants and spend more on them than what is normally spent. Aboo Hurayrah :ra: reports that Rasoolullah (peace be upon him) said, "One who generously spends on his family on the day of Ăshooră, Allah will increase (his provision) for the whole year." (Bayhaqi, at-Targheeb wat-Tarheeb)

This Hadeeth is not very authentic according to the science of Hadeeth. However, scholars of Hadeeth like Bayhaqi and Ibne Hibbăn have accepted it as reliable.